Vibration sensors are used, for example, as knock sensors in internal combustion engines. European Patent No. 0 184 666, for example, describes such a knock sensor, which is diagramed in FIG. 4. The knock sensor has a housing 2 and a pressure sleeve 3 on whose outside are arranged a piezoceramic disk 4 and a seismic mass 5 acting on it. Seismic mass 5 acts on piezoceramic disk 4 by way of a plate spring 6. The prestress on plate spring 6 is produced by a threaded ring 7 screwed onto the pressure sleeve. Pressure sleeve 3 therefore has an outside thread 8. The force applied to piezoceramic disk 4 may therefore be adjusted and limited as desired. Piezoceramic disk 4 is situated between two contact disks 9, these contact disks 9 being connected to a cable 11 by wires 10.
The arrangement described above for holding together the individual parts of the knock sensor by way of the threaded ring and the plate spring has the disadvantages that it is relatively expensive to manufacture and can also lead to manufacturing defects. In particular in the manufacture of outside thread 8 on pressure sleeve 3, shavings from cutting the thread, for example, may fall into the interspace between pressure sleeve 3 and piezoceramic element 4 when screwing on threaded ring 8. Therefore, a short circuit may occur after the sheathing has been extruded onto housing 2.
In addition, European Patent No. 0 184 666 describes the fastening of plate springs 6 by using a Seeger ring.
In addition, German Patent No. 195 24 152 describes a vibration sensor which has on the outside of the pressure sleeve bulges which function as a stop for the plate spring. These bulges are produced by caulking of the material of the pressure sleeve. However, inaccuracies in the prestress of the piezoceramic disk over the plate spring may occur here due to uneven caulking.